Local area networks (LANs) are commonly connected to one another through one or more routers so that a host (a workstation such as a PC, data center server, or other arbitrary LAN entity) on one LAN can communicate with other hosts on a different LAN (that is, remote or external networks). Typically, a host is able to communicate directly only with the entities on its local LAN segment. When it needs to send a data packet to an address that it does not recognize as being local, it communicates through a router (or other layer-3 or gateway device) which determines how to direct the packet between the host and the destination address in a remote network. A data center environment, which may include many hosts spanning multiple geographical sites, is an example of one such environment.
Unfortunately, a router may, for a variety of reasons, become inoperative after a power failure, reboot, scheduled maintenance, or other event. Such potential router failure has led to the development and use of redundant systems. Accordingly, a data center interconnect may have more than one gateway device to provide a back up in the event of primary gateway device failure. When a gateway device fails in such a redundancy system, the host communicating through the inoperative gateway device may still remain connected to other LANs by sending packets to and through another gateway device connected to the host's LAN.
Various protocols and techniques have been devised to allow a host to choose a router from among a group of routers in a network. Certain of these protocols allow each host to be dynamically assigned to a gateway device such that multiple gateway devices in a redundancy group simultaneously handle traffic. Hosts may be assigned to a router by random or round robin assignment or according to load balancing techniques.
Often a non-local router is assigned to a host. As a result, network traffic from the host traverses the data center interconnect. Such traffic is highly inefficient as it contributes to additional bandwidth cost of the data center interconnect and higher traffic latencies. Additionally, where the gateway devices are virtual machines that may move locales within the data center environment, the relocation of a host may result in traffic traversing the data center.
Accordingly, the ability to provide a communications system that consumes few resources, optimizes bandwidth, and achieves superior performance in a data center environment presents a significant challenge for network operators, service providers, and system administrators.